Original Posted By: Ken Beanlands
Subject: Pietenpol-List: more gross weight>Don't antbody yell at me for this,mechanics about gross weight. He told me that gross weight is mostlydetermined by how much weight the aircraft's landing gear can support. Hefurther said that most airplanes can lift more weight than the gross, butthe landing gear, on landing just can't support it.>>There is a very interesting story in a book about the history of the c-47.It seems that one of these airplanes was used in the Berlin airlift to haula gross weight load of aluninum matting. After needing the entire runway fortakeoff, the airplane never was able to get much out of ground effect, andhad to fly into Berlin at full power just to stay in the air. After landingand unloading , it was discovered that the aluminum matting was actually afull load of steel.>>As I recall, the airplane was ok, but the landing gear was messed up.>>>http://www.mailexcite.com________________________________________________________________________________
Pietenpol-List: more gross weight
Pietenpol-List: Re: more gross weight
Original Posted By: LanhamOS(at)aol.com
Subject: Pietenpol-List: Re: more gross weight>Among other interesting comments, Mike Cunningham observed:>>>>I left Addison Tx. Last eve. in a C172 with full fuel and just 2 aboard.>Got>>a real close-up view of the Galleria south>>of the airport and just barely made our assigned alt. of 2000 feet>>in the Class B above Love Field. This airplane was a couple hundred>>pounds under gross.>>Brings up a couple of questions. What was the temperature at the time?>And do you think it would have been all that difficult if you had been>taking off in, say, New Hampshire in January?>>Owen Davies>________________________________________________________________________________
Subject: Pietenpol-List: Re: more gross weight>Among other interesting comments, Mike Cunningham observed:>>>>I left Addison Tx. Last eve. in a C172 with full fuel and just 2 aboard.>Got>>a real close-up view of the Galleria south>>of the airport and just barely made our assigned alt. of 2000 feet>>in the Class B above Love Field. This airplane was a couple hundred>>pounds under gross.>>Brings up a couple of questions. What was the temperature at the time?>And do you think it would have been all that difficult if you had been>taking off in, say, New Hampshire in January?>>Owen Davies>________________________________________________________________________________
Pietenpol-List: more gross weight
Original Posted By: Greg Yotz
Don't antbody yell at me for this, There is a very interesting story in a book about the history of the c-47. It seemsthat one of these airplanes was used in the Berlin airlift to haul a grossweight load of aluninum matting. After needing the entire runway for takeoff,the airplane never was able to get much out of ground effect, and had to flyinto Berlin at full power just to stay in the air. After landing and unloading, it was discovered that the aluminum matting was actually a full load of steel.As I recall, the airplane was ok, but the landing gear was messed up.http://www.mailexcite.com________________________________________________________________________________
Don't antbody yell at me for this, There is a very interesting story in a book about the history of the c-47. It seemsthat one of these airplanes was used in the Berlin airlift to haul a grossweight load of aluninum matting. After needing the entire runway for takeoff,the airplane never was able to get much out of ground effect, and had to flyinto Berlin at full power just to stay in the air. After landing and unloading, it was discovered that the aluminum matting was actually a full load of steel.As I recall, the airplane was ok, but the landing gear was messed up.http://www.mailexcite.com________________________________________________________________________________
Pietenpol-List: Re: more gross weight
Original Posted By: Michael D Cuy
Sounds like your friend is listening in his A&P classes...Ramp weight, or "MaxTaxi Weight" is that weight above the max take off weight that the landinggear will support without damage. Max Take Off Weight is that weightdetermined by the power available and the lift available. Power Loading andWing Loading are familiar terms, but usually used in a slightly differentcontext. Basically, if the wing has a "loading" of, say, 6 pounds per squarefoot, that means that that wing/airfoil combination can safely support thatmuch weight. For instance, a 24 foot wing with a 48 inch (4 foot) chord hasthat 6 pound loading, you can safely move 576 pounds into the loweratmosphere. Raise the weight, either through making the airplane heavier, orincreasing g-loads, and you can flirt with disaster. Stall speeds increaseuntil they overcome the available lift. Then you can only go one way...down.The take off weight, although having a "fudge factor", is nothing for theaverage pilot to play with, unless his insurance is paid in full, he haskissed his wife good-bye, and the IRS is snipping at his heels. Beforeanybody calls me to task for this statement by saying, "but what about ol' so-and so, who took off over gross on his non-stop trip hither and yon?", let mesay that if he was successful he either did a lot of homework or had an angelon his shoulder. Even Charles Lindberg almost didn't get off the ground goingto Paris, and an awful lot of his contemporaries didn't make it beyond thetrees. Power loading? A door will fly with enough horsepower aboard to drag itaround. Look at the space shots, and their MILLIONS of pounds of thrust toinject them into space. We ain't that lucky. Don't even think about it. Ed ________________________________________________________________________________
Sounds like your friend is listening in his A&P classes...Ramp weight, or "MaxTaxi Weight" is that weight above the max take off weight that the landinggear will support without damage. Max Take Off Weight is that weightdetermined by the power available and the lift available. Power Loading andWing Loading are familiar terms, but usually used in a slightly differentcontext. Basically, if the wing has a "loading" of, say, 6 pounds per squarefoot, that means that that wing/airfoil combination can safely support thatmuch weight. For instance, a 24 foot wing with a 48 inch (4 foot) chord hasthat 6 pound loading, you can safely move 576 pounds into the loweratmosphere. Raise the weight, either through making the airplane heavier, orincreasing g-loads, and you can flirt with disaster. Stall speeds increaseuntil they overcome the available lift. Then you can only go one way...down.The take off weight, although having a "fudge factor", is nothing for theaverage pilot to play with, unless his insurance is paid in full, he haskissed his wife good-bye, and the IRS is snipping at his heels. Beforeanybody calls me to task for this statement by saying, "but what about ol' so-and so, who took off over gross on his non-stop trip hither and yon?", let mesay that if he was successful he either did a lot of homework or had an angelon his shoulder. Even Charles Lindberg almost didn't get off the ground goingto Paris, and an awful lot of his contemporaries didn't make it beyond thetrees. Power loading? A door will fly with enough horsepower aboard to drag itaround. Look at the space shots, and their MILLIONS of pounds of thrust toinject them into space. We ain't that lucky. Don't even think about it. Ed ________________________________________________________________________________
Pietenpol-List: Re: more gross weight
Original Posted By: oil can
I won't yell at you but I will say flatly that your "student of mechanics"friend is way off base. Let's go to Denver Co. (or North Little Rock, Ar.for that matter) on a hot summer day and rent us a Cessna 150, load it up togross weight and go fly. Believe me, this will really get your attention!The amount of runway needed, the marginal climb performance and the sickfeeling you get looking at the mountains up ahead can really get the hairson your neck to stand up!Now lets put another 100 lbs in it (about 20%overload). If you get this pup offthe ground by the end of the runway then your problems have just begun andbending the gear will be the least of your worries.I left Addison Tx. Last eve. in a C172 with full fuel and just 2 aboard. Gota real close-up view of the Galleria southof the airport and just barely made our assigned alt. of 2000 feetin the Class B above Love Field. This airplane was a couple hundredpounds under gross.My point is that aircraft landing gear is designed to take some prettyhard landings (2-3 G's ? I don't know, somebody do the math) but a few extrapounds on board has meant the end of many an airplane, pilot, andpassengers. Weight and balance figures are based on flight performance andsafety. Take them very seriously.-----Original Message-----
I won't yell at you but I will say flatly that your "student of mechanics"friend is way off base. Let's go to Denver Co. (or North Little Rock, Ar.for that matter) on a hot summer day and rent us a Cessna 150, load it up togross weight and go fly. Believe me, this will really get your attention!The amount of runway needed, the marginal climb performance and the sickfeeling you get looking at the mountains up ahead can really get the hairson your neck to stand up!Now lets put another 100 lbs in it (about 20%overload). If you get this pup offthe ground by the end of the runway then your problems have just begun andbending the gear will be the least of your worries.I left Addison Tx. Last eve. in a C172 with full fuel and just 2 aboard. Gota real close-up view of the Galleria southof the airport and just barely made our assigned alt. of 2000 feetin the Class B above Love Field. This airplane was a couple hundredpounds under gross.My point is that aircraft landing gear is designed to take some prettyhard landings (2-3 G's ? I don't know, somebody do the math) but a few extrapounds on board has meant the end of many an airplane, pilot, andpassengers. Weight and balance figures are based on flight performance andsafety. Take them very seriously.-----Original Message-----
Pietenpol-List: Re: more gross weight
Original Posted By: Owen Davies
If you think that landing gear is all that limits gross weight, you areover simplifying the problem. During the initial design process, a missionprofile for the given aircraft is defined. For example, a 40 pax. twinturbo prop capable of 5 hrs cruise at 250 kts. This means a passengerpayload of 43 (pax+crew) x passenger weight (assuming 170 lbs) or 7130 lbsplus thier luggage (50 lbs x 43) or 2150 lbs for a payload of 9280 lbs.The design cruise will be determined and a suitable airfoil/planformselected. This will help determine power requirements and rough fuelpayloads. Assuming 2 x 2000 hp @ .5 specific fuel consumption gives about1600 lbs per hour or, for a 5 hr endurance, approximately 8000 lbs. Thisgives a usable of 17280 lbs. Now that the usable is frozen, the emptyweight can be estimated. Let's say that turn's out to be 24,000 lbs. Thisis when the aerodynamics are re-checked to see if a gross weight of 41,280lbs will work. Adjustments are made and the empty weight is frozen. Each system and structure is given weight restrictions from the weightsengineers. Using limit and yeild load factors specified in the FAR's,parts are designed to support the gross weight + load factors. Thisapplies to ALL structures, not just the landing gear. For example, thewing is designed to support the gross weight x 4.4 (limit load) x 1.5(safety factor) for a total of 272448 lbs (positive). Other criteria arealso considered here such as control forces (torsional stiffness), dragforces, fatigue, etc. which may end up making the airplane capable ofcarrying heavier weights at slow speeds.The landing gear is designed to withstand 20G (if I remember correctly) atthe maximum landing weight. This weight can only differ from the Max TOweight if the airplane is equipped to dump fuel. The idea is that 99.9% ofthe time, an airplane will land significantly lighter than it takes off,so wy carry all the extra weight in the landing gear to support a landingat max TO weight. So, by exceeding the gross weight, you could end up running into otherdesign limits before you ever get a chance to land. One example that comesto mind was a video I saw of a prototype European twin (simular to a TwinCommander) that was being flown at an airshow by the factory test pilot. The plane was designed utilizing the latest in finite element analysis andother computer design tools such that the structure would withstand thelimit load plus the safety factor and nothing more making it a veryeffecient design. This was fine except that the pilot was from the"old-school" of thinking where the planes structures were always strongerthan the published umtimate load factors. During the aerobaticperformance, both wings broke at exactly the same time and within 1% ofthe ultimate load. When you consider the number of experienced engineers that are designingcomponents to withstand the ultimate loading at the least amount ofweight, it is hard to say just where a plane will fail when pushed outsidethese limits. Ken________________________________________________________________________________
If you think that landing gear is all that limits gross weight, you areover simplifying the problem. During the initial design process, a missionprofile for the given aircraft is defined. For example, a 40 pax. twinturbo prop capable of 5 hrs cruise at 250 kts. This means a passengerpayload of 43 (pax+crew) x passenger weight (assuming 170 lbs) or 7130 lbsplus thier luggage (50 lbs x 43) or 2150 lbs for a payload of 9280 lbs.The design cruise will be determined and a suitable airfoil/planformselected. This will help determine power requirements and rough fuelpayloads. Assuming 2 x 2000 hp @ .5 specific fuel consumption gives about1600 lbs per hour or, for a 5 hr endurance, approximately 8000 lbs. Thisgives a usable of 17280 lbs. Now that the usable is frozen, the emptyweight can be estimated. Let's say that turn's out to be 24,000 lbs. Thisis when the aerodynamics are re-checked to see if a gross weight of 41,280lbs will work. Adjustments are made and the empty weight is frozen. Each system and structure is given weight restrictions from the weightsengineers. Using limit and yeild load factors specified in the FAR's,parts are designed to support the gross weight + load factors. Thisapplies to ALL structures, not just the landing gear. For example, thewing is designed to support the gross weight x 4.4 (limit load) x 1.5(safety factor) for a total of 272448 lbs (positive). Other criteria arealso considered here such as control forces (torsional stiffness), dragforces, fatigue, etc. which may end up making the airplane capable ofcarrying heavier weights at slow speeds.The landing gear is designed to withstand 20G (if I remember correctly) atthe maximum landing weight. This weight can only differ from the Max TOweight if the airplane is equipped to dump fuel. The idea is that 99.9% ofthe time, an airplane will land significantly lighter than it takes off,so wy carry all the extra weight in the landing gear to support a landingat max TO weight. So, by exceeding the gross weight, you could end up running into otherdesign limits before you ever get a chance to land. One example that comesto mind was a video I saw of a prototype European twin (simular to a TwinCommander) that was being flown at an airshow by the factory test pilot. The plane was designed utilizing the latest in finite element analysis andother computer design tools such that the structure would withstand thelimit load plus the safety factor and nothing more making it a veryeffecient design. This was fine except that the pilot was from the"old-school" of thinking where the planes structures were always strongerthan the published umtimate load factors. During the aerobaticperformance, both wings broke at exactly the same time and within 1% ofthe ultimate load. When you consider the number of experienced engineers that are designingcomponents to withstand the ultimate loading at the least amount ofweight, it is hard to say just where a plane will fail when pushed outsidethese limits. Ken________________________________________________________________________________
Pietenpol-List: Re: more gross weight
Original Posted By: oil can
Among other interesting comments, Mike Cunningham observed:>I left Addison Tx. Last eve. in a C172 with full fuel and just 2 aboard.Got>a real close-up view of the Galleria south>of the airport and just barely made our assigned alt. of 2000 feet>in the Class B above Love Field. This airplane was a couple hundred>pounds under gross.Brings up a couple of questions. What was the temperature at the time?And do you think it would have been all that difficult if you had beentaking off in, say, New Hampshire in January?Owen Davies________________________________________________________________________________
Among other interesting comments, Mike Cunningham observed:>I left Addison Tx. Last eve. in a C172 with full fuel and just 2 aboard.Got>a real close-up view of the Galleria south>of the airport and just barely made our assigned alt. of 2000 feet>in the Class B above Love Field. This airplane was a couple hundred>pounds under gross.Brings up a couple of questions. What was the temperature at the time?And do you think it would have been all that difficult if you had beentaking off in, say, New Hampshire in January?Owen Davies________________________________________________________________________________
Pietenpol-List: Re: more gross weight
Original Posted By: Owen Davies
Since this has been the second hottest summer on record in TexasI am pretty sure everybody realizes that two of the "three H's" (hot, high,humid) were definitely in effect. Temp was about 100 and humidity probably75% or more. I'll take winter in NH any time (actually they can keep it-) ) but I still would not even consider overloading the airplane. I guessmy point here is that summer flying in TX often gives us an up close andpersonal demonstration of aircraft performance limits that others may notexperience as often. We take weight, balance limits and the "three h's" veryseriously, and know that thereis no gray area to play with. Sure you might get away with over-loading aplane on a cold day, but you are becoming a test pilot. Then you get to findout about other things (Do you have enough elevatorto flair for landing?, etc.). There are a hundred reasons not to overloadan airplane, bending the gear is way, way towards the bottom of the list.-----Original Message-----
Since this has been the second hottest summer on record in TexasI am pretty sure everybody realizes that two of the "three H's" (hot, high,humid) were definitely in effect. Temp was about 100 and humidity probably75% or more. I'll take winter in NH any time (actually they can keep it-) ) but I still would not even consider overloading the airplane. I guessmy point here is that summer flying in TX often gives us an up close andpersonal demonstration of aircraft performance limits that others may notexperience as often. We take weight, balance limits and the "three h's" veryseriously, and know that thereis no gray area to play with. Sure you might get away with over-loading aplane on a cold day, but you are becoming a test pilot. Then you get to findout about other things (Do you have enough elevatorto flair for landing?, etc.). There are a hundred reasons not to overloadan airplane, bending the gear is way, way towards the bottom of the list.-----Original Message-----